1. Field of the Invention
In general, this invention relates to components for a sprinkler system; more particularly, it relates to a valve that installs in a riser of a sprinkler system and provides two valve functions: one being to stop flow automatically when breakage of a sprinkler head causes the flow rate to exceed a predetermined threshold; and the other being to prevent back flow and reduce the risk of the "hammer effect" causing damage to the sprinkler system.
2. Description of the Prior Art
Automatic sprinkler systems are widely used to irrigate lawns and landscape areas surrounding residential, commercial property, and in municipal parks, golf courses, and along highways.
Such a sprinkler system is designed to carry water under pressure through supply line piping into riser pipes which can be located above or below ground level and then through sprinkler heads or nozzles where the water flow is transformed into a desired spray. The size and number of sprinkler heads in a system depend upon available water pressure. Normally, the system is divided into irrigation zones consisting of a given number of sprinkler heads. The flow of water to these various zones is normally controlled by off and on manual or electronic solenoid valves which can be activated manually or by automatic timer controls.
In such a sprinkler system, the water supply lines are generally made of plastic or metal and conform to standard diameters such as 1/2", 3/4" or 1". Plastic or metal tees or elbows are used to interconnect the supply lines. The tees and elbow connectors are connected to plastic or metal riser pipes through each of which a portion of the water flows to the sprinkler heads and nozzles which are available in different flow rates and irrigation spray and coverage patterns.
Two of the most costly and common problems that plague the operation of such a sprinkler system are referred to herein as the "broken riser" problem and the "hammer effect."
As for the broken riser problem, the costs attributable to this problem include the following. In addition to providing a means of controlling the spray pattern distribution of water, the nozzle orifices are sized in order to restrict the flow rate of the water in gallons per minute. If the sprinkler head is damaged or removed or the riser pipe is broken the flow restriction capability of the nozzle is also removed. Loss of the flow rate restriction feature results in an immediate virtually unrestricted flow of water at the damaged sprinkler. The flow rate at the damaged sprinkler head or riser is restricted only by the diameter of the remaining portion of the broken riser (typically 1/2", 3/4" or 1" in diameter). A single broken riser or one with a missing sprinkler head can flow at rates from 30 to 100 gallons per minute depending upon the water pressure of the affected system. Undetected and unrestricted flow of water for thirty to forty minutes can result in the loss of 900 to 4,000 gallons of valuable water which in turn can cause extensive erosion, flooding and create the potential for damage, injury and loss of life and property if the water is projected into traffic onto near by streets and highways by the geyser or high pressure fountain effect.
In addition, damage to the sprinkler head or riser always results in an immediate substantial drop in water pressure in the other sprinkler heads on the supply line in that zone and renders them ineffective. Costly emergency repairs are often required and the entire system must be shut down in order to repair and or replace the damaged components or until time and available parts can be obtained to make the necessary repairs. Loss of irrigation even for a couple of days can result in the loss of valuable lawns or water dependent landscaping due to lack of moisture.
As for the "hammer effect" problem, this is a problem which may ultimately cause failure of an entire sprinkler system. The "hammer effect" is a result of back flow at the end of an irrigation cycle when the water is turned off. When the water is turned off the water remaining in the system drains to the lowest point in the line and fills the supply line with air, when the water is turned on during the next irrigation cycle water flows under pressure into the supply line forcing the air trapped in the system out and at the precise moment that the air is purged from the supply line the resulting in a momentary high pressure shock known as the "hammer effect" and produces high stress pressure on the entire branch of the supply lines and sprinkler heads. This event is created every time the water is turned on in the system. Eventually the "hammer effect" which severely stresses the entire system will lead to damage of the supply lines resulting loss of irrigation capacity for a period of time and expensive repairs or replacement.
A prior art patent that describes the "broken riser" problem is U.S. Pat. No. 4,842,198 (the '198 patent). The '198 patent describes a device that is installed between a distribution tee and a riser. The device of the '198 patent appears to be intended to provide a single valve that turns off automatically in response to a pressure drop change, and do so under control of a damping force caused by a dashpot. Although the filing date of the '198 patent is more than six years ago, the "broken riser" problem has not been solved by any commercialized device, and the "hammer effect" problem likewise has not been adequately addressed.